Got my printer working almost perfectly. However, I’m going nuts trying to get the little bump at the seam to go away. I have tossed around the settings for retraction, print speed, extrusion width, and anything else I could think of, to no avail. Anyone experienced this before, or have any suggestions?
That’s a Z scar caused by the printer pausing when it retracts at the end of each layer. You can spread the dots out by setting your slicer to start each layer at random points rather than whatever makes for fastest print speeds. To get rid of them you need to turn on coasting which will stop extruding a set length before the end of the layer to relieve the pressure in the nozzle so you don’t get blobs when you retract.
I usually print with, and prefer, random points, but then they are all over. Didn’t have this issue until about a month ago, however, my quality has gone up greatly, so they were likely hidden before. Is there a way to have Slic3r coast? I know Simplify 3D does, but when i try to run gcode from it, the printer freezes up when the hotend reaches temp.
Bowden setup? Make sure the tube is seated securely and doesnt move during retraction.
@PrintinAddiction Thank you for the suggestion, just fixed that two days ago. While it probably made some tiny difference, it didn’t solve the bumps. My bowden tube is only about 14 inches from extruder to hotend. 
I had the same issues on my prusa, and it was a combination of random start points, wipe on retract, and bump the retraction speed and distance.
I have my retraction speed at 40mm/s and a length of 8mm. I’ve tried the wipe on retract, but sometimes it leaves ugly marks. 
@Adam_Steinmark Sorry, forgot to make my reply a reply. xP
I agree 3mm coast is probably the best fix for this. But you could also try retract speed 150mm/s or more, and/or reducing retract length from 8 to 5 or even 3mm, this will help reduce dwell time during retract. If you get too many strings with shorter retraction, try reducing hotend temperature by 10 degrees. Also some slicers have an option to randomize perimeter starting point over 60 or 90 degrees angle, so it’s not one obvious seam line, but still no bumps on the front side of your print.
@Johann_Rocholl Thank you for the advice, I will try some of it asap. As for the coast setting, Slic3r doesn’t have one.
I’d say coasting will fix this problem. I’ve been using simplify3D only for a while now, but if I remember correctly, I had negative number in extra length after retract setting in slic3r and that was a solution for a similiar problem.
@Topias_Korpi Trying that negative “after retract length” right now, with faster retract speeds. I’d love to try Simplify3D, but it never works with my Robo. Gets to temp and just hangs.
With retraction at 3mm/-0.5 and speed at 80mm/s, no improvement or any noticeable difference. :S
@Aric_Norine The Slic3r settings I have for acceleration are on default. Do you have a recommended setting I could try?
I’m new to this… But since I use the LIN_ADVANCE from the Marlin firmware, problems like this go away (also with slic3r)
@Karl_Schlacher What is this LIN_ADVANCE that you speak of? ^^
I use Marlin firmware. Since about 3 month they made a new way to print (LIN_ADVANCE). The pressure over hole length of a segment is konstant (sharp edge,…) - also when you use same speed for all elements (perimeter, infill…)
… sry for my bad english
How about using internal start for each layer? It’s an option in Cura.
I think coast = wipe, just different naming in different slicers. Basically the nozzle moves during a retraction so any oooze is stretched over a larger area. At least thats my understanding of it.
@PrintinAddiction They are different. Coast stops extrusion before the perimeter is ended and wipe just does extra movement during retraction.